Voltage controlled oscillators (VCO) are used in a number of circuits including phase lock loops (PLL) for example, which in turn can be used in radio tuning, multiplexer synthesisers, or clock extraction in optical fibre receivers for timing reference for example. To ensure low cost and minimal component count, the VCO is preferably realised as a fully integrated design of the PLL. However the demands of PLL performance such as low jitter, low power supply pushing, and high temperature stability often force PLL designers to use a more costly external voltage controlled crystal oscillator, making the PLL, more difficult and costly to manufacture.
Many electronic components now operate at reduced supply voltages, for example 3V, which makes them more susceptible to supply and temperature pushing. Current integrated VCO which compensate for such temperature and power supply variations have met with limited success and are discussed in more detail below.